Method of removing insulation from metallic electric conductors



meme Sept. 7, 1948 METHOD OF REMOVING INSULATION FROM METALLIC ELECTRIC CONDUO'IOIS Yaro Plskao and Raymond E. Smiley, Maple Heights, Ohio, asaignss'a, by asesne alignments. to Jack & Ileinta Preehlols Industries, Inc., Cleveland, Ohio, a corporation of Delaware No Drawing. Application April 21, 1045. Serial No. 500.1

2 Claims. (Cl. 184-38) The present invention relates to the removal of and the like and has for its primary object to provide a simple, effective and inexpensive process of chemically removing coatings of high dielectric strength and tough adhering characteristics as found in certain types of varnishes used for insulating purposes.

In practice it will be realized that it may be necessary to remove such insulation either locally to make electric connections or over a length of wire. or the like. when for example, the insulation has been damaged. The conventional practice has been to mechanically remove such insulation by scraping but this practice is laborious and time consuming and often results in irreparable damage to the conductor.

The present invention contemplates the convenient and expeditious removal of the insulation by a chemically active agent. There is a particularly effective insulation of high dielectric properties known in the trade as "Formvar." which is a vinyl acetate resin. It is a synthetic material, more-or-less in the nature of a plastic. and is used for coating electric conductors as an improvement over other known enamels used for insulating purposes. This material is extremely sticky and adhesive and diillcult to apply. Such insulated conductors have found extensive use for the windings of generators, starter "motors and the like and the Formvar" insulation has been found to be extremely difficult to remove. It will be appreciated that the conventional procedure in applying such an insulation to a conductor is to apply it to the full length of the conductor. Subsequently. in order to make proper electrical connections. certain portions of the conductor must necessarily have its insulation removed. Besides removal of the varnish. dirt and organic material from the conductor the metallic surface should be removed and the surface of the conductor rendered clean and unimpaired and amiable for fusing as well as for electric current yin p poses- 7 As a result of research and experimentation the present invention specifically contemplates for optimum results the use of an aqueous solution of a concentration of four pounds of chromium trioxide (CrOa) per gallon at a temperature of 221' Fahrenheit. The limit range of operation should preferably be kept within 10 to 14 grams 4 .of chromium trioxide per 25 cubic centimeters at 2 from 190' to 226 Fahrenheit. The optimum result under the preferred conditions above mentioned is the removal of insulation having characteristics comparable with that of Formvar within a period not exceeding 30 seconds.

Thus single wires or other conductors or a plurality thereof having Formvar insulation thereon may have any desired length adjacent their terminals, or in fact their entire length if desired. dipped into this solution at the preferred temperature and have the insulation quickly and thoroughly removed without damage to the conductor or its metallic surface.

We claim:

1. The method of removing insulation of vinyl acetate resin material from metallic electric conductors which comprises forming an aqueous solution of from ten to fourteen grams per 25 cubic centimeters of chromium trioxide, heating so said solution to a temperature within a range or from 190' to 226 Fahrenheit and immersing a portion of said conductor with its insulation in said solution for a period of time approximating thirty seconds to remove said insulation without ll damage to said conductor or its metallic surface.

2. The method of removing insulation of vinyl acetate resin material from metallic electric conductors which comprises forming an aqueous solution of four pounds per gallon of chromium trioxide, heating said solution to a temperature of 221 Fahrenheit and immersing a portion or said conductor with its insulation in said solution for a period of time approximating thirty seconds to remove said insulation without so damage to said conductor or its metallic surface.

YARO PISKAC. RAYMOND E. SMILEY.

cas crran The following references are of record in the die of this patent:

UNI'IID STATES PATENTS unm- "Modern Inorganic Chemistry." Longmans. Green and Ca. N. Y.. 1980 (page 71: relied on) (Copy in Division 31.) 

